Rectifying system for high-tension alternating currents.



J. H. LENDI. v RECTIFYlNG SYSTEM FOR HIGH TENSION ALTERNATINGWCU RRENTS.Patented July17, 1917'.

3 SHEETS-SHEET I.

APPLICATION FILED JANJM I9I6.

J. H. LENDI. RECTIFYING SYSTEM FOR HIGH TENSION ALTERNATING CURRENTS.

, APPLICATION FILED JAN.24, I916. 1,234,099. Patented July 17, 1917.

3 SHEETS-SHEET 2.

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PATENT OFFICE.

JOHN H. LENDI, or CHICAGO, ILLINOIS.

RECTIFYING SYSTEM FOR HIGI-LTENSION ALTERNATING CURREN'IS.

Specification of Letters Patent.

Patented July 1'7, 1917.

Application filed January 24, 1916. Serial No. 73,903.

7 '0 all whom it may concern:

Be it known that I, JOHN H. LENDI, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented a new and Improved Rectifyin System for High-TensionAlternating (Iurrents, of which the following is a specification.

My invention relates to a rectifying system for high tension alternatingcurrents characterized by the use of commutating devices or otherrectifying means connected with the high tension side of a polyphasesource of high tension alternating current, by which a substantiallyconstant unidirectional current is delivered to the main conductors usedto supply high tension unidirectional current for any desired purpose.My system while particularly adapted to use in connection with dustprecipitation devices is not, however, limited to this use, but may beemployed for any purpose in connection with which it is necessary tohave high tension uni-directional current of substantially constantvalue. By my invention I combine the high tension waves delivered fromthe high tension windings of the polyphase transformer so as to mosteffectively utilize the waves in the combined uni-directional current.

My invention will best be understood by reference to the drawings inwhich Figure 1 is a diagrammatic drawing showing one form of myrectifying system in its entirety,

Fig. 2 shows in a diagrammatic drawing a modified arrangement of thecommutating devices,

Fig. 3 shows in a diagrammatic drawing an arrangement of currentrectifying devices for carrying out my invention,

Fig. 1 shows in a diagrammatic drawing a rectifying system in which therectified high tension waves are delivered to the unidirectional supplyconductors in series relation,

Fig. 5 shows in a diagrammatic drawing a modified arrangement of currentrectifying devices for combining the high tension waves in seriesrelation,

Fig. 6 shows in a diagrammatic view an arrangement of dust collectingmechanism for use in connection with the rectifying system,

Fig. 7 is a detail View of one of the commutating devices,

Fig. 8 is a drawing of the curves of the various electric motive forcesof the several phases and the resultant curves of electromotive forceproduced by my rectifying system, and

Fig. 9 is a detail view of one of the rectifying devices that I preferto employ in carrying out my invention.

Similar numerals refer to similar parts throughout the several views.

In order to better understand the open ation of my system in whichcurrent rectifying devices are employed, refer first to the rectifyingmechanism shown in Fig. 9, which is a device known as a kenetron andwhich consists of a glass globe 10 containing in it a first electrode 11in the form of a cup partly within which is located a hot wire electrode12, the terminals of which are connected by wires 13 and 14 which extendthrough one of the arms of the tube. being hermetically sealed therein.The cup 11 is connected by a conductor 15 with an external terminal ofthe tube being hermetically sealed in the other arm thereof so that thewire 15 and the wire 13 outside of the tube constitute the terminals tobe connected to the high tension source of alternating current. Betweenthe wires 13 and 14 outside of the tube a battery 16 and variableresistance 17 are connected in series for the purpose of maintaining thehot wire electrode 12 in heated condition. The tube is exhausted to avery high degree. the vacuum obtained being as nearly perfect aspossible, and for this condition it has been found that current flowwill only take place from the anode 11 to the cathode 12 when the latteris highly heated, this effect being due to a thermionic discharge givenoff by the highly heated cathode. I find such a device to beparticularly elfective in rectifying high tension alternating currents,for the reason that it completely prevents the passage of current fromthe electrode 12 to the electrode ll and there is therefore no danger ofbreaking down the gap between the electrodes by high tension waves whichare negative relatively to the anode and cathode referred to. Thekenetron construction described is not of itself my invention and Itherefore make no claim for it apart from the combination in which it isemployed in carrying out my system, for my invention consists in thecombination wlth the terminals of a high tension polyphase source ofalternating current of commutating and rectifying devices of which thekenetron may be a part to'secure the results to be described.

In the system shown in Fig. 1 a threephase alternating current generator18 is shown having conductors 19, 20 and 21 extending therefrom todeliver the three-phase current to the primary windings 22, 23 and 24 ofthe transformers A, B and C, these primary windings being deltaconnected and the winding 22 being connected between the .conductors 19and 20, the winding 23 be;

tween the conductors 19 and 21 and the winding 24 being connectedbetween the conductors 21 and 20. But one of the threephase generatingwindings is shown in connection with the generator 18, but as is wellknown in the art it will be understood that the other two generatingwindings are similar to the one shown and displaced therefrom and fromeach other by 120 electrical degrees.

The secondary windings of the transformers A, B and C are shown at 25,26 and 27 respectively, and these secondary windings which are the hightension windings are delta connected and are also connected to the hightension conductors a, b and c, the secondary winding 25 being connectedbetween the conductors 0 and a, the secondary winding 26 being connectedbetween the conductors a and b and the secondary winding 27 beingconnected between the conductors b and c. It will be understood that theconductors a, b and 0 are typical of any high tension three-phase supplysystem and for purposes of comparison the supply conductors in Figs. 2and 3 are similarly designated.

The shaft 28 of the generator has mounted upon and insulated from it sixcommutating arms 29, 30, 31, 32, 33 and 34 which are arranged in pairs,the arms 29 and 30 of one pair having one angular position and the arms31, 32 and 33, 34 of the other pairs being displaced from the first pairand from each other by 120 degrees. These commutating arms coiiperatewith commutating segments 35, 36, 37, 38, 39 and 40 respectively, eachbeing of substantially 120 de grees in extent, the segments 35, 37 and39 being similarly disposed angularly and connected together byconductors 41 and 42 with the high tension positive conductor 43 whilethe other segments 36,38'a-nd 40 are in the same angular positionrelatively to each other, but displaced substantially 120 degrees fromthe segments 35, 37 and 39, the segments 36, 38 and 40' being connectedto the negative 44 of the high tension unidirectional source of supply.

The commutating arms 29, 30, 31, 32, 33 and 34 are supplied withalternatingcurrent by the slip rings 45, 46, 47, 48, 49 and 50 uponwhich rest the brushes 51, 52, 53, 54, and 56 respectively.

The brush 51 is connected by wire 57 through kenetron 58 with theconductor a; the brush 52 is connected by wire 59 through kenetron 60with conductor a; the brush 53 is connected by wire 61 through kenetron62 with conductor 0,- the brush 54 is connected by Wire 63 throughkenetron 64 with conductor 0; the brush 55 is connected by wire 65through kenetron 66 with conductor 5, and the brush 56 is connected bywire 67 through kenetron 68 with conductor 7). The kenetrons referred toare connected in the several wires so that current flow may occurthrough them only in the direction indicated by the arrow heads forminga part of the diagrammatic representations of the kenetrons.

Referring to Fig. 8 the waves of alternating clectromotive forcesdelivered from the transformer windings 25, 26 and 27 are shown at a, Z)and 0 respectively. The arms carried by the shaft 28 are disposedrelatively to the waves of electromotive force delivered from thegenerator 18 and the commutator segments are so disposed relatively tothe arms that the commutating devices are effective in completing thecircuit from the secondary windings of the transformers A, B and C asindicated by the disposition of the diagrammatic representations of thecommutator bars in Fig. 8, that is to say, the segments 35 and 38 areeffective in completing the circuit from the secondary winding 25 forthe middle 120 degrees of the positive waves of the electromotive forcea, the segment 39 and 36 are effective in closing the circuit from thesecondary winding 26 during the middle 120 degrees of the positive wavesof the electromotive force 5', and the segments 37 and 40 are effectivein closing the circuit from the secondary winding 27 during the middle120 degrees of the positive waves of the electromotive force 0. In otherwords, the middle 120 degrees of each positive current wave of the threephases is delivered to the positive conductor 43 and supplied thereby tothe devices employed for utilizing the unidirectional current and isreturned by the other main or negative conductor 44 to the secondarywinding from which it is delivered, and the curve of rectified currentthus supplied to the circuit, including the conductors 43 and 44, isshown at X in Fig. 8.- It is to be borne in mind that as a result of thedelta connection of the secondary windings 25, 26 and 27 the followingoperation is taking place at all times: Considering simply the closedcircuit formed by the series arrangement referred to, the algebraic sumof the instantaneous values of the electromotive forces is at all timesZero and therefore during any interval when current delivered from oneof the secondary windings is being communicated to the conductors 43 and44 the algebraic sum of the electromotive forces developed in the othertwo secondary windings is equal in amount at any instant to theelectromotive force in the winding delivering the current to theconductors 43 and 44 and opposite in direc tion and as a result of theconnection of the conductors a, b and 0 above described, at any timethat .one of the secondary windings is effective in sending positivecurrent Waves to the circuit including the conductors 43 and 44 theother two secondary windings are effective also in delivering currentthrough the same path, and therefore all of the secondary windings-areeffective at all times in supplying current to the commutating devicesand to the conductors 43 and 44. For example, when the secondary winding25 is sending positive current through conductor a, arm 29 and segment35 to the conductor 43 this conductor (6 is the negative terminal of thecombined secondary windings 26 and 27, the other terminal being theconductor 0, which conductor is the negative terminal at this time forthe secondary winding 25. At this time the algebraic sum of theelectromotive forces in the secondary windings 26 and 27 must benegative and equal in amount to the electromotive forces in the winding25 in' order that the algebraic sum of all of the electromotive forcesdeveloped in all three windings may be zero, and therefore for thiscondition the secondary windings 26 and 27 are together effective indelivering to the positive conductor a an amount of currentsubstantially equal to that delivered to said conductor by the secondarywinding 25. The operation of the several secondary windings referred toso that they are at all times eflective in delivering current to becommutated as a result of the parallel relation of the secondarywindings relatively to the conductors extending to the commutatingdevices is, as far as I am aware, novel and eliminates the necessity ofspecial commutating devices for inverting the negative waves ofelectromotive force developed in the secondary windings, for, as will beobserved in connection with Figs. 1 and 8, the commutating arms andsegments are provided in my system only in connection with the positivewaves of electromotive force developed by the several secondarywindings.

While the commutating arms are described above as being carried by theshaft 28, it will of course be understood that this arrangement is shownfor the sake of simplicity and that I do not limit myself to thisconstruction, but that I may employ any other arrangement by which thecommutating arms may be operated synchronously with the rotor of thegenerator.

1V hile any desired form of commutating devices may be used which willcommunicate the middle 120 degrees of each positive wave ofelectromotiveforce to the direct current conductors, I find itconvenient to employ for this purpose the construction shown in detailin Fig. 7 in which a disk 69 of insulating material, such for example asgutta percha or other similar material having high dielectric strengthis employed, which disk is mounted upon the shaft provided to rotate thesame and carries at its outer edge outwardly projecting inclined flanges70 and 71 between which a conducting ring 72 is mounted. This conductingring 72 constitutes the slip ring construction referred to in connectionwith Fig. 1 and in practice is en gaged by any suitable conducting brushfor communicating the current to said ring. The disk 69 has projectingoutwardly from one side of it just inside of one of the flanges referredto a boss 73 in which is mounted a conducting rod 74 electricallyconnected with the ring 72, this rod 7 4 constituting one of thecommutating arms shown diagrammatically in Fig. 1. The rod 74 cooperateswith a conducting segment 7 5 supported from the base of the machine bya disk 76 of insulating material of high dielectric strength provided atits outer edge with inturned flange 77 extending around the boss 73 andinside of the flange 71. The segment is connected with the circuits ofthe system as described above and each is of substantially 120 degreesextent for the system shown and described in connection with Fig. 1. Itwill be understood that my system contemplates the generation of veryhigh electromotive forces, such, for example, as 100,000 volts or overand that for these electromotive forces it is unnecessary to have therod 74 make contact with the segment 75 to close the circuit by means ofthe commutating devices, although substantially the same constructionmay be employed for lower voltages if desired by bringing the segmentclose enough to the rod so that it makes contact with the end of saidrod as it rotates.

One of the purposes for which the high tension unidirectional currentdelivered by the system shown in Fig. 1 may be employed is indicated inFig. 6, and consists in devices for precipitating dust as follows: Achamber 7 8 is provided across which a plurality of rods 79 extend,these rods being" to the other electric terminal 82 of the device, thelatter terminal being preferably grounded as indicated. The dust ladengas is delivered into the chamber through the inlet opening 83 acrossthe rods 79 between the plates 81 and the condition of electro staticstress produced by the electrodes in the chamber serves to separate thedust from the air, after which the cleaned air is discharged from thechamber through the stack 84. The terminals 80 and 82 are connected withthe high tension direct current wires 43 and 44 shown in Fig. 1.

The degree to which the rectified current produced by the system shownin Fig. 1 may be made to approach a constant value is determined by thenumber of phases employed in the system. As stated above, with athreephase system the rectified current has the form indicated at X inFig. 8 and the lowest value is that shown at the points a For asix-phase system the middle sixty degrees of each rectified wave remainsthe same, and these parts of the waves of rectified current areconnected by similar waves as indicated at Y in Fig. 8, the lowestvalues of the rectified current now being the points y. For a 12-phasesystem the middle 30 degrees of each rectified current wave of thesix-phase system remains as in the six-phase system, and these Waves areconnected by similar waves Z as indicated in Fig. 8, the lowest valuesof the rectified current being now I serve the important purpose ofpermitting current flow in but one direction in the several paths inwhich they are employed, and in addition they protect the commutatingdevices by preventing the application of high electromotive forces uponthe commutating devices until such times as the devices should come intooperation. For example, when the commutating arm 29 has nearly completedits 120 degrees. of operative rotation opposite the segment 35 the arm30 approaches the segment 36 and were the kenetron 60 not present in thewire 59 the same electromotive force impressed upon the arm 29 would beimpressed upon the arm 30, with the result that there might readily be ajumping of the current from the arm 30 to the segment 36 and thus to thenegative conductor 44 which would in large part defeat the operation ofthe rectifying system as a whole. Permitting as they do current flow inbut one direction, the kenetrons serve as a protection to the rectifyingsystem, and it will be understood that these kenetrons may be used inmultiple groups to any extent that may be necessary to carrythe-necessary amount of curr nt to be rectified.

For conditions in which the potential of the rectified current may belower than above referred to and where there is no danger of the currentjumping across relatively wide gaps from the commutating arms to theirsegments, the arrangement shown in Fig. 2 may be employed, in which theconductors a, b and c are connected directly to the brushes 51, 52, 53,54, 55 and 56. this system being in all respects identical with thatshown in Fig. 1 with the exception that the kenetrons are omitted fromthe various circuits.

If preferred, for certain conditions, particularly those requiring but asmall current flow, the commutating devices above described may bedispensed with and kenetrons alone may be used to rectify the polyphasehigh tension alternating current. Such a system is showndiagrammatically in Fig. 3 in which the conductors a, Z), and c areconnected to wires 85, 86 and 87 respectively, the wire 85 beingconnected with the negative terminal of the kenetron 88 and the positiveterminal of the kenetron 89, the wire 86 being connected with thenegative terminal of the kenetron 90 and the positive terminal of thekenetron 91 and the Wire 87 be ing connected with the negative terminalof kenetron 92 and the positive terminal of kenetron 93. The positiveterminals of the kenetrons 88, 90 and 92 are connected together and tothe positive conductor 43* by which rectified current is supplied to thedevices to be operated by the system, and the negative terminals ofthe'kenetrons 89, 91 and 93 are connected together and to the conductor44 of the rectifying current system.

It will be understood that whether the arrangement shown in Figs. 1, 2or 3 be employed the current is rectified as shown diagrammatically inFig. 8, and that the operation of the secondary windings 25, 26 and 27is the same ineach case.

The system thus far described may be called a multiple rectifying systemfor the 7,

reason that the electromotive force impressed upon the supply conductorsby which rectified current is communicated to the desired devices is ofthe same amount as that delivered from each of the secondary windings ofthe polyphase transformer or transformers. My system of rectification isalso applicable to a series arrangement of the secondary windings ofthese transformers and embodiments of my invention in seriesarrangements are shown in Figs. 4 and 5.

In Fig. 4 the secondary windings 25 26 and 27 for the polyphase currentto be rectified are shown, the primary windings and source of currentsupply being omitted for the sake of clearness, which primary windingsand source are of any desired construction and may be the same as shownin Fig. 1. The winding 25 is connected by brushes with slip rings 91 and95, which in turn are connected with the commutating arms 96, 97 and 98,99 respectively, the arms 96, 97 and 98, 99 cotiperating with thesemicircular commutator segments 100, 101, 102 and 103 respectively, thearms 96 and 97 being oppositely disposed relatively to their segments100 and 101 as are also the arms 98 and 99 relatively to their segments102 and 103. The secondary winding 26 is similarly connected to sliprings 101, 105, commutating arms 106, 107, 108 and 109 and commutatingsegments 110, 111, 112 and 113 and the secondary winding 27 is similarlyconnected with slip rings 114, 115, commutating'arms 116, 117, 118 and119, and commutator segments 120, 121, 122 and 123, the only differencebeing that the commutator segments for the winding 27 are displacedrelatively to the commutator segments for the winding 25 120 degrees,and that the commutator segments for the winding 26 are displacedrelatively to the commutator segments for the winding 25 240 degrees,this displacement corresponding to the displacement between the phasesof the threephase current being rectified It will be understood that thedisplacement referred to between the several commutator segments may besecured by any desired arrangement of the commutator arms and segments,whether the arms for the several windings are in the same angularposition relatively to each other as shown in Fig. 4 or not, the onlyrequirement being that the commutating action shall be displaced foreach secondary winding relatively to the other secondary windings in amanner corresponding with the displacement of the phases of thealternating current being rectified.

The positive conductor 43 for supplying rectified current is connectedby wires 121 and 125 with segments 123 and 120 respectively; thesegments 121 and 122 are connected together by wire 126, which wire alsoconnects these segments with the segments 110 and 113, and the segments111 and 112 are connected together by wire 127, which also connectsthese segments with the segments 100 and 103. The segments 101 and 102are connected together by wire 128, which is also connected with thenegative conductor 41 of the circuit for supplying rectified currentfrom the system. As a result of the connections described the arm 96serves to communicate positive waves of current from the secondarywinding 25 to the wire 127, the return path for these waves being fromnegative conductor all" to segment 102 to arm 98; the arm 106 serves tocommunicate positive waves of current from the positive winding 26 tothe wire 126, the return path for these waves being through thecommutating device connected with the secondary winding 25 to wire 127,and thus to segment 112 and arm 108; and the arm 116 serves tocommunicate positive waves from the secondary winding 27 to the wire 125and thus to the positive conductor 43, the return path for these wavesbeing in series through the commutating devices connected with thesecondary windings 25 and 26 to wire 126 and thus to segment 122 and arm118. Similarly the arm 99 serves to de liver negative current waves fromthe secondary winding 25 to wire 127, the return path for these wavesbeing from the negative conductor 11 to wire- 128 to segment 101 andthus to arm 97; the arm 109 serves to deliver negative waves from thesecondary winding 26 to the wire 126, the return path for these wavesbeing through the commutating devices connected with the wind ing 25 towire 127 to segment 111 and thus to arm 107; and the arm 119 serves todeliver negative waves from the secondary winding 27 to the wire 121 andthus to the positive supply wire 43 ot' the rectifying current system,the return path for these waves being from conductor 11 in seriesthrough the commutating devices connected with the secondary windings 25and 26 to the wire 126 to segment 121 and thus to arm 117. From theconnections it will appear that the electromotive forces developed inthe secondary windings 25, 26 and 27 are always connected in series andin such a manner that the tendency to produce current flow by thoseelectromotive forces is always in the same direction, the sum of theefiective electromotive forces being at all times impressed upon thesupply conductors 13" and 11 of the rectifying current system in such adirection as to send current out through the conductor 43 and toconstitute the conductor 11 a return path for the rectified current ofthe system. The series commutating system just described may be employedfor potentials which are not sufliciently high to cause improperoperation of the commutating devices, and for a rectifying system inwhich it is desirable to use much higher potentials I find it desirableto employ lrenetrons without the use of commutating devices, as, forexample, in the arrangement shown in Fig. 5. In this arrangement thesecondary windings of the polyphase supply transformers are shown at 2526 and 27 The secondary winding 25 is connected by wire 129 withpositive terminal of the kenetron 130 and the negative terminal of thekenetron 131, and by wire 132 with the positive terminal of thelrenetrun 133 and the negative terminal of the kenetron 134; thesecondary winding 26 is connected by wire 135 with the positive terminalof the kenetron 136 and the negative kenetron 140, and the secondarywinding 27 is connected by wire 141 with the positive terminal of thekenetron 142 and the negative terminal of the kenetron 143 and by wire144 with the positive terminal of the kenetron 145 and the negativeterminal of the kenetron 146.

The negative terminals of the kenetrons 130 and 133 are connectedtogether by wire 147 to which the negative conductor 44 of therectifying system is connected. The positive terminals of the kenetrons131 and 134 are connected together by wire 148 and the negativeterminals of the kenetrons 136 and 139 are connected together by wire149. The wires 148 and 149 are connected together by wire 150. Thepositive terminals of kenetrons 137 and 140 are connected together bywire 151 and the negative terminals of kenetrons 142 and 145 areconnected together by wire 152. The wires 151 and 152 are connectedtogether by wire 153. The positive terminals of kenetrons 143 and 146are connected together by wire 154, which is also connected to thepositive conductor 43 of the rectifying system. As a result of theconnections described, assuming the direction of positive waves in thesecondary windings to be upward, a positive current wave from thesecondary winding 25 flows through wire 132, kenetron 134 to wire 148and thus to wire 150, from which the current fiows in parallel pathsthrough the kenetrons 139, 140 and 136, 137 to wire 153 from which thecurrent flows in parallel paths through the kenetrons 145, 146 and 142,143 to the supply conductor 43 of the rectifying system. The return pathfor these positive 1 waves is from conductor 44 to wire 147,

kenetron 130 to wire 129 and thus back to the secondary winding 25.Similarly the path for current flow of positive waves from the secondaryWinding 26 is through wire 138, kenetron 140, wire 151 to wire 153 andfrom thence in parallel paths through kenetrons 145, 146 and 142, 143 tothe positive supply conductor 43, the return path for these waves beingconductor 44 in parallel paths through kenetrons 133, 134 and 130, 131to wire 150 to wire 149, kenetron 136 to wire 135 back to secondarywinding 26 Similarly the path for current flow of positive waves fromthe secondary winding 27 is by wire 144 to kenetron 146, wire 154 to.supply conductor 43, the return path for these waves being conductor 44in parallel paths through kenetrons 133, 134 and 130, 131 to wire 150,from thence in parallel paths through kenetrons 139, 140 and 136, 137 towire 153 to wire 152, kenetron 142, wire 141 back to secondary winding27. The path for the flow of negative waves from the secondary winding25 is as follows: wire 129, kenetron 131, wire 148, wire 150 and thencein parallel paths through kenetrons 139, 140 and 136, 137 to Wire 153,and thence in parallel paths through kenetrons 145, 146 and 142, 143 topositive supply conductor 43, the return path for these waves being fromconductor 44 to wire 147, kenetron 133, wire 132, back to secondarywinding 25. The path for the flow of negative waves from thesecondarywinding 26 is by wire 135 to kenetron 137, wire 151, wire 153,thence in parallel paths through kenetrons 145, 146 and 142, 143 topositive supply conductor 43, the return path for these waves being fromconductor 44 in parallel paths through kenetrons 133, 134 and 130, 131to wire 150, thence by wire 149 to kenetron 139 to wire 138, and thenceback to secondary winding 26. The path for the flow of negative Wavesfrom secondary winding 27 is by wire 141 to kenetron 143, wire 154,thence to positive supply conductor 43, the return path for these wavesbeing from conductor 44 in parallel paths through kenetrons 133, 134 and130, 131 to wire 150, thence in parallel paths through kenetrons 139,140 and 136, 137 to wire 153, thence to wire 152, kenetron 145, wire 144back to secondary winding 27. The paths described, it Will be seen,afford a series connection between the secondary windings 25, 26 and 27,such that the electromotive forces of these windings are at all timescombined'additively so that the numerical sum of their instantaneousvalues and not their algebraical sum is impressed upon the mainconductors 43 and 44 of the rectifying system.

While I have shown my system in the embodiments disclosed in Figs. 4 and5 as employed for the purpose of rectifying 3-phase high tensionalternating current, the waves of the different phases being at anyinstant connected together in series, it will be under-' stood that thisarrangement is equally applicable to a larger number of phases and thatas the number of phases increases the reaction due to sending thecurrent through the secondary windings which at any particular instantmay be developing but small electromotive forces relatively, iscorrespondingly reduced.

From the above it will appear that I have provided arectifying system bywhich alternating current of very high voltage may be rectified whetherof single or polyphase, and further that my system provides a means forrectifying polyphase alternating current in a manner to get the fulleffect at any instant of all of the current waves with out providingseparate rectifying or commutating devices for the negative waves fromthose employed for the positive waves. For certain purposes, such forexample as the precipitation of dust by corona or static discharge aunidirectional current is required of very high potential and foreffective operation this unidirectional current must be of practicallyconstant value in order to maintain the operation of the precipitatingdevice since the precipitation occurs only above a certain limitingvalue of potential, and the effectiveness of the precipitation devicesis much greater than it would be with an intermittent high potentialrectified current, such for example, as might be obtained from asingle-phase alternating current. On account of the very high potentialemployed in my system it is impracticable to use ordinary rectifyingdevices, such for example,

as electrolytic rectifiers or quench tubes since they do not affordprotection for current flow in reversed direction through them for thevoltages employed in my system. The kenetrons referred to, however, areadmirably adapted to this purpose since their resistance to current flowin a direction opposite to that for which they are designed ispractically infinite, and it is therefore practically impossible toforce current to flow through them from the heated cathode to the anode.

WVhile I have shown the transformers employed in connection with mysystem as delta connected, it will be understood that the primary andsecondary windings of the transformers may be either star connected ordelta connected as desired or that a combination of the two may beemployed without interfering with the operation of my system, theprincipal difference being that with the star connection of thesecondary windings as for example in certain embodiments of my system asshown in Fig. 1 the high tension sources are no longer connectedtogether in parallel relation and that therefore during any period ofrectification but one current path through the source is effective insupplying current to the rectifying and commutating devices.

While I have shown my invention in the particular embodiments abovedescribed, it will be understood, however, that I do not limit myself tothese particular constructions as I may employ equivalents thereofwithout departing from the spirit of my invention.

What I claim is:

1. In a high tension commutator, the combination of a disk of insulatingmaterial, a conducting arm projecting from said disk, a slip ringcarried by said disk, an insulating base, and a conducting commutatingsegment secured to said base for cooperation with said arm.

2. In a high tension commutator, the combination of a disk of insulatingmaterial, a

conducting arm projecting from said disk, a slip ring carried by saiddisk, an insulating base, and a conducting commutating segment securedto said base for cooperation with said arm, said disk having aninsulating flange extending from it between said slip ring and saidcommutating arm.

3. In a high tension commutator, the combination of a disk of insulatingmaterial, a conducting arm projecting from said disk, a slip ringcarried by said disk, an insulating base, and a conducting commutatingsegment secured to said base for cooperation with said arm, said basehaving an insulating flange extending from it around said arm and saidsegment.

4. In a high tension commutator, the combination of a disk of insulatingmaterial, a conducting arm projecting from said disk, a slip ringcarried by said disk, an insulating base, and a conducting commutatingsegment secured to said base for cooperation with said arm, said diskhaving an insulating flange extending from it between said slip ring andsaid commutating arm, and said base having an insulating flange extending from it around said arm and said segment.

5. In a system for rectifying high tension alternating current, thecombination of a plurality of polyphase supply conductors for deliveringalternating current at high potential, two commutating devices angularlydisplaced to correspond with the angular displacement of two of thephases and connected with each supply conductor by branch connectionsone for current flow in each direction through said supply conductor,and conductors connected with said commutating devices for receivingunidirectional current therefrom, said commutating devices beingoperative for current waves of but one and the same sign for the severalphases.

6. In a system for rectifying high tension alternating current, thecombination of a plurality of polyphase supply conductors for deliveringalternating current at high potential, two commutating devices angularlydisplaced to correspond with the angular displacement of two of thephases and connected with each supply conductor by branch connectionsone for current flow in each direction through said supply conductor,conductors connected with said commutating devices for receivingunidirectional current therefrom, said commutating (16-. vices beingoperative for current waves er but one and the same sign for the severalphases, and a delta connected source of polyphase current connected withsaid supply conductors.

7. In a system for rectifying high tension alternating current, thecombination of a plurality of polyphase supply conductors.

for delivering alternating current at high potential, two commutatingdevices angularly displaced to correspond with the angular displacementof two of the phases and connected with each supply conductor by branchconnections one for current flow in each direction through said supplyconductor, conductors connected with said commutating devices forreceiving unidirectional current therefrom, said commutating devicesbeing operative for current waves of but one and the same sign for theseveral phases, and a polyphase step up transformer having deltaconnected secondary windings connected with said supply conductors.

8. Ina system for rectifying high tension alternating current, thecombination of a plurality of polyphase supply conductors for deliveringalternating current at high potential, two commutating devices angularlydisplaced to correspond with the angular displacement of two of thephases and connected with each supply conductor by branch connectionsone for current flow in each direction through said supply conductor,conductors connected with said commutating devices for receivingunidirectional current therefrom, said commutating devices beingoperative for current waves of but one and the same sign for the severalphases, and oppositely connected current valves in the branchconnections from each supply conductor, whereby when current flowsthrough a supply conductor and the current valve in one of its branchconnections the current valve it its other branch connection bypreventing current fiow through said other branch connection preventsimpressing the potential of said supply conductor upon the commutatingdevice connected with said other branch connection.

9. In a system for rectifying high tension alternating current, thecombination of a plurality of polyphase supply conductors for deliveringalternating current at high potential, two commutating devices angularlydisplaced to correspond with the angular displacement of two of thephases and connected with each supply conductor by branch connectionsone for current flow in each direction through said supply conductor,conductors connected With said commutating devices for receivingunidirectional current therefrom, said commutating devices beingoperative for current waves of but one and the same sign for the severalphases, op-

positely connected current valves in the branch connections from eachsupply conductor, whereby when current flows through a supply conductorand the current valve in one of its branch connections the current valvein its-other branch connection prevents impressing the potential of saidsupply conductor upon the commutating device connected with said otherbranch connection,

and a delta connected source of polyphase current connected with saidsupply conductors.

10. In a system for rectifying high tension alternating current, thecombination of a plurality of polyphase supply conductors for deliveringalternating current at high potential, two communicating devicesangularly displaced to correspond with the angular displacement of twoof the phases and connected with each supply conductor by branchconnections one for current fiow in each direction through said supplyconductor, conductors connected with said commutating devices forreceiving unidirectional current therefrom, said commutating devicesbeing operative for current waves of but one and the same sign for theseveral phases, oppositely connected current valves in the branchconnections from each supply conductor, whereby when current flowsthrough a supply conductor and the current valve in one of its branchconnections the current valve in its other branch connection preventsimpressing the potential of said supply conductor upon the commutatingdevice connected with said other branch connection, and a polyphase stepup transformer having delta connected secondary windings connected withsaid supply conductors.

11. In a system for rectifying high tension alternating current, thecombination of a plurality of polyphase supply conductors for deliveringalternating current at high potential, two commutating devices angularlydisplaced to correspond with the angular displacement of two of thephases and connected with each supply conductor by branch connectionsone for current flow in each direction through said supply conductor,conductors connected with said commutating devices for receivingunidirectional current therefrom, said commutating devices beingoperative for current waves of but one and the same sign for the severalphases, and oppositely connected kenetrons in the branch connectionsfrom each supply conductor, whereby when current flows through a supplyconductor and the kenetron in one of its branch connections the kenetronin its other branch connection by preventing current flow through saidother branch connection prevents impressing the potential of said supplyconductor upon the commutating device connected with said other branchconnection.

12. In a system for rectifying high tension alternating current thecombination of a plurality of polyphase supply conductors for deliveringalternating current at high potential, two communicating devicesangularly displaced to correspond with the angular displacement of twoof the phases and connected with each supply conductor by branchconnections one for current flow in each direction through said supplyconductor, conductors connected with said commutating devices forreceiving unidirectional current therefrom, said commutating devicesbeing operative for current waves of but one and the same sign for theseveral phases, oppositely connected kenetrons in the branch connectionsfrom each supply conductor, whereby when current flows through a supplyconductor and the kenetron in one of its branch connections the kenetronin its other branch connection prevents impressing the potential of saidsupply concluctor upon the commutating, device connected with said otherbranch connection, and a delta connected source of polyphase currentconnected with said supply conductors.

13. In a system for rectifying high tension alternating current, thecombination of a plurality of polyphase supply conductors larlydisplaced to correspond with the angular displacement of two of thephases and connected with each supply conductor by branch connectionsone for current flow in each direction through said supply conductor,conductors connected with said commutating devices for receivingunidirectional current therefrom, said cormnutating devices beingoperative for current waves of but one and the same sign for the severalphases, oppositely connected kenetrons in the branch connections fromeach supply conductor, whereby when current flows through a supplyconductor and the kenetron in one of its branch connections the kenetronin its other branch connection prevents impressing the potential of saidsupply conductor upon the commutating device connected with said otherbranch connection, and a polyphase step up transformer having deltaconnected secondary windings connected with said supply conductors.

In witness whereof, I hereunto subscribemy name this 17th day ofJanuary, A. D.

JOHN H. LENDI.

